The present invention relates to a polymer compound which contains a thermoplastic elastomer, or more specifically it relates to a thermoplastic elastomer compound with superior reinforcing characteristics as well as with either electrical conductivity or electrical insulating characteristics, produced by compounding ultra-fine carbon fibrils.
Recently, there is an increasing demand for electrically conductive or electrically insulating polymer materials used in electronic parts or semiconductive layers of power cables for the purpose of preventing static generation or interferences from external electromagnetic waves.
Conventionally, the method of filling electrically conductive carbon-black in a matrix polymer has been used as a way to add electrically conductive characteristics to a rubber. Although it achieves the desired electrical conductivity, the method fails to reinforce the strength of the material. On the other hand, the system of adding reinforcing type carbon-black results in the desired reinforcing effect when as much as 30-100 phr is filled (wt. parts against 100 wt. parts of rubber). However, the system is absolutely ineffective in increasing electrical conductivity.
Incidentally, both reinforcing and electrically conductive effects can be obtained by compounding chopped carbon fibers which possess both of these effects. However, such fiber is not necessarily a satisfactory reinforcing material because of its poor molding characteristics, the poor surface appearance of the molded products, and anisotropic nature. Moreover, its reinforcing effects depend on the processing conditions since its short fibers break during the processing.
Recently, ultra-fine carbon fibrils became available, and the possibility of compounding such carbon fibrils in a resin or rubber-like polymer has been discussed. However it has been difficult to obtain a material with well balanced properties including suitable hardness and superior elasticity.
The present invention intends to offer a thermoplastic elastomer compound which possesses a reinforcing effect and both electrically conductive and electrically insulating effects, as well as balanced strength and elasticity.